class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        set<int> s1(nums1.begin(), nums1.end());
        set<int> s2(nums2.begin(), nums2.end());
        vector<int> ret;
        auto it1 = s1.begin();
        auto it2 = s2.begin();
        while (it1 != s1.end() && it2 != s2.end()) {
            if (*it1 == *it2) {
                ret.push_back(*it1);
                it1++;
                it2++;
            }
            else if (*it1 < *it2) {
                it1++;
            }
            else if (*it2 < *it1) {
                it2++;
            }

        }
        return ret;
    }

};